As a substrate processing apparatus, there has been widely known a plasma processing apparatus which performs a predetermined process such as etching on a substrate by using plasma. The plasma processing apparatus includes a depressurizable processing chamber capable of generating plasma therein and accommodating a substrate such as a wafer for a semiconductor device; a mounting table (a susceptor) positioned in the chamber to mount the substrate thereon; an electrostatic chuck (ESC) positioned on an uppermost portion of the susceptor to hold the wafer; an upper electrode positioned above the ESC and facing the ESC at a certain distance to supply a processing gas into the chamber; and a focus ring (F/R) positioned in an upper outer periphery of the susceptor to surround the wafer.
The ESC is made of, for example, a circular plate-shaped ceramic member and includes therein an electrostatic electrode connected to a DC power supply. If a positive DC voltage is applied to the electrostatic electrode, a negative potential is generated on a rear surface (on the ESC side) of the wafer mounted on the top surface of the ESC, so that a potential difference is generated between the electrostatic electrode and the rear surface of the wafer W and thus the wafer is attracted to and held on the ESC by Coulomb force or Johnsen-Rahbek force caused by the potential difference.
Typically, the ESC has one size smaller diameter than the wafer mounted on the ESC, and, thus, there is a small gap between an outer periphery of the ESC and the rear surface of the wafer. Further, a CF polymer, which is a reaction product of a CF-based processing gas used in a plasma process, may be deposited as a deposit (hereinafter, simply referred to as “deposit”) in this gap. A deposit deposited on, particularly, a shoulder of the outer periphery of the ESC (hereinafter, referred to as “shoulder deposit”) may cause an error in attracting the wafer W onto the ESC, and, thus, the shoulder deposit may become a hindrance to a satisfactory plasma process. Particularly, in plasma etching using a substrate processing apparatus, a tendency to use a processing gas having a high deposition property becomes stronger, and, thus, a shoulder deposit becomes a serious problem.
Accordingly, there has been a need to remove a shoulder deposit as quickly as possible so that, conventionally, a shoulder deposit has been removed by a person. However, this method is inefficient in that whenever the shoulder deposit needs to be removed, a chamber needs to be open to the atmosphere. Therefore, recently, there has been employed a dry cleaning method capable of decomposing and removing the shoulder deposit by using oxygen (O2) plasma without opening the chamber to the atmosphere. However, a region right above the outer periphery of the ESC is shielded by the wafer, and, thus, ions in the plasma cannot reach the outer periphery from the above. Therefore, the shoulder deposit may not be efficiently removed.
Meanwhile, a CF-based shoulder deposit generated from a CF-based processing gas could be removed by using the oxygen (O2) plasma, but a shoulder deposit containing a metal such Al or Si from the wafer or members in the chamber in addition to the CF could not be removed by using the oxygen plasma. Accordingly, it has been known that the CF-based shoulder deposit containing Si or Al can be decomposed and removed by using plasma generated from a mixed gas of an O2 gas and a fluorine (F) containing gas. As one example of a chamber cleaning method using plasma generated from a F containing gas, there has been disclosed a cleaning method in which an inductive plasma is generated within a chamber while introducing a fluorine containing gas into the chamber and an inside of the chamber is cleaned by the inductive plasma (see, for example, Patent Document 1).
Patent Document 1: Japanese Patent Laid-open Publication No. 2003-151971
However, when the inside of the chamber is cleaned by the plasma generated from the fluorine containing gas, a surface of the ESC made of, for example, Al2O3 is exposed to F radicals and thus eroded. Further, the upper electrode made of Si or SiC is exposed to the F radicals, and, thus, its surface becomes rough. Accordingly, so-called “black silicon” is formed on the upper electrode.
The present disclosure provides a chamber cleaning method capable of efficiently removing a CF-based deposit containing at least one of Si and metal and deposited on an outer periphery of an electrostatic chuck.
Further, the present disclosure provides a chamber cleaning method capable of removing a CF-based deposit containing at least one of Si and metal and deposited on an outer periphery of an electrostatic chuck without eroding a surface of the electrostatic chuck while preventing surface roughness of the upper electrode.